According to a new market report published by Transparency Market Research "Big Data Market - Global Scenario, Trends, Industry Analysis, Size, Share and Forecast, 2012 - 2018" the global big data market was worth USD 6.3 billion in 2012 and is expected to reach USD 48.3 billion by 2018, at a CAGR of 40.5% from 2012 to 2018. North America is expected to maintain its lead position in terms of revenues till 2018, with about 54.5% share of the global big data market revenue, followed by Europe.

Nitin,
I've added a link to Wikibon's Big Data Market forecast. Not sure what your definition is, our figures don't agree. We either have a wider net or are more bullish and other analyst firms that I've read also have higher numbers than you do. Care to share any additional information or a comparison of how your methodology and numbers compare with ours?